Modeling of Thermal Properties of Thermal Insulation Layered with Transparent,Opaque and Reflective Film

The popular and effective food preservation technology based on refrigeration is not sufficient for high-quality products while undergoing logistic operations (transport and retail). One of the basic factors that affects the quality of chilled and frozen food products during storage and transport is packaging. A protective function of packaging strongly depends on the material used and its composition. There are different kinds of thermal insulation used for food packaging. One of them, proposed by the authors is a multilayer structure of insulation made of rectangular air cells. The insulation can be prepared by means of plastic film featuring various properties. The paper presents how to improve an effective material designed for food freezing and transport aiming to enhance its thermal resistance through the application of different transparency, reflectivity and emissivity of the film. Mathematical model based on heat exchange equations, including conduction, convection and radiation throughout a number of parallel internal sheets of film of multilayer structures was proposed. Thermal properties depending on different transparency, reflectivity and emissivity of the film were analyzed. The model was verified experimentally showing its compatibility and obtaining a significant influence of thermal resistance according to the type of film used to make air structures, the number and thickness of its layers as well as the gaps between internal folds. For multi-layer insulation designed for the insulation of packed frozen food in the shape of a rectangle, it was recommended to apply film transmittance as small as possible for the internal parts of the structure.     

Surface integrity of Mg-based nanocomposite produced by Abrasive Water Jet Machining (AWJM)

This paper investigates the influence of jet traverse speed on the surface integrity of 0.66?wt% Al₂O₃ nanoparticle reinforced metal matrix composite (MMC) generated by Abrasive Water Jet Machining (AWJM). Surface morphology, surface topography, and surface roughness (SR) of the AWJ surface were analyzed. The machined surfaces of the nanocomposites were examined by laser confocal microscope and field emission scanning electron microscope (FESEM). Microhardness and elasticity modulus measurement by nanoindentation testing were also performed across thickness of the samples to see depth of the zone, affected by AWJ cutting. The result reveals that extent of grooving by abrasive particle and irregularity in AWJ machined surface increases as the traverse speed increased. Similarly, the rise in value of surface roughness parameters with traverse speed was also seen. In addition, nanoindentation testing represents the lower hardness and elastic modulus due to softening occurs in AWJ surface.     

Electro-optical properties of diluted GaAsN on GaAs grown by APMOVPE

In this paper we report on the optical and electrical studies of single GaAs_1?x N _x epitaxial layers grown on GaAs substrates by means of atmospheric pressure metal organic vapour phase epitaxy (APMOVPE). Three kinds of samples with 1.2 %, 1.6 % and 2.7 % nitrogen content were studied. Optical properties of the layers were investigated with the use of room temperature transmittance and reflectance measurements. Subsequently Schottky Au-GaAs_1?x N _x contacts were processed and characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements within 80–480 K temperature range. From the I-V and C-V characteristics the ideality factor, series resistance and built-in potential were determined. Obtained diodes can be used for further studies on defects with the use of DLTS method.     

A view from inside onto the surface of self-assembled nanocomposite coatings

Hybrid organic–inorganic (O–I) nanocomposite coatings with an O–I matrix and inorganic nanofillers were synthesized by two consecutive and independent processes: sol–gel process (build-up of inorganic structures with epoxide-functions in situ) and polyaddition reaction (epoxy network formation with amines). Two O–I matrices were prepared: the GTMS–D400 type exhibits a high degree of regularity and self-ordering in the bulk (inorganic domains separated by elastic D400 chains) while in the GMDES–T403 type a linear inorganic polyepoxide is homogeneously mixed with the amino component without any separated inorganic domains. Inorganic nanofillers (natural or chemically modified montmorillonites and colloidal silica) differing in size and shape, were added to the matrices. Core properties of the composite products, on sub-micrometer and micrometer levels were studied by solid-state NMR spectroscopy, transmission electron microscopy, and wide-angle X-ray scattering. Macroscopic, bulk properties of the materials were investigated by static and dynamic mechanical analysis. The gas transport properties of the prepared coatings were tested with hydrogen and oxygen. The surface morphology of the coatings with and without nanofillers was determined by atomic force and scanning electron microscopy. A high degree of self-organization existing already in the O–I matrix was observed in some cases, which obviously influences the self-assembly behaviour of the nanofillers in the O–I matrix and on the surface of the hybrid coatings.     

水平管道水力输送粗粒物料的阻力损失研究

以深海采矿固液两相流管道输送工艺为应用背景，通过建立管道水力输送模拟系统，研究了不同粒径、不同体积浓度、不同输送速度条件下粗颗粒在水平管道中的阻力损失的变化规律。试验结果表明：颗粒浓度越高，输送速度越大，阻力损失越大。阻力损失与各参数的主要关系有：在保持其他条件不变的情况下，阻力损失与浓度或速度呈指数关系；颗粒运动状态对阻力的变化率有一定的影响。基于试验数据并结合理论分析，提出了阻力损失计算公式。     

Analytical study on cofactor biorecognition by immobilized alkaline apophosphatase

Alkaline apophosphatase (apoALP) was examined in flow bioanalytical systems as an immobilized bioligand for reversible recognition of zinc ions. For such investigations plastic open-tubular bioreactor coupled with spectrophotometric detector and potentiometric biosensor based on plasticized polymeric membrane ion-selective electrode were applied. Both biodevices contain covalently immobilized monomolecular layer of alkaline phosphatase (ALP) and operate according to the indirect biosensing scheme based on cofactor biorecognition by in situ generated apoenzymatic bioreceptor. An implementation of immobilized ALP into flow system enables automation of the developed bioanalytical procedure allowing multiple and reproducible apoenzyme formation/regeneration, analyte biorecognition as well as assays for recovered enzyme activity. Both developed bioanalytical systems offer relatively fast zinc biodetermination in the ppm range of concentrations. Additionally, effects from potential chelators and metal ions involving in holo-apo and apo-holo enzyme conversions were investigated. It was found, that the selectivity of the reported biosensing scheme is defined by alternative mechanisms for apoenzyme and holoenzyme formation. A model, clarifying such conversions, has been proposed and confirmed by simple analytical experiments performed under flow conditions.